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A490 TC Bolts For High Strength Construction Applications

A490 TC bolts are used in many heavy structural applications. These bolts are made to install quickly and to self-calibrate. One of their most notable qualities is a built-in tension control element, which is called the spline. This is why they are known as tension control bolts or twist-off bolts.

These bolts are compliant with ASTM A490 specification as set by the American Society for Testing and Material standards organization. This spec pertains to structural bolts with a hex head. They have a diameter range between 1/2 inch and 1 1/2 inches. The threaded length of these bolts is shorter than non-heavy-duty and standard bolts, which contributes to a robust and reliable hold between steel connections. The minimum tensile strength of these bolts is 150,000 psi.

A490 TC bolts are similar to A325 TC bolts with the exception of the standard material used in their manufacturer. A490 TC bolts are made with alloy steel while A325 TC bolts are made of medium carbon steel. A490 TC bolts will therefore provide higher strength capabilities compared to those made to the A325 spec.

Many of the advantages of A490 TC bolts are a direct result of their form, which is integral to the speed and consistency of their installation method. TC bolts are almost always provided as a fastener assembly, which includes the bolt itself, a washer, and a nut. The end of the bolt has a spline or “twist-off”.

TC bolts are installed using an electric tool called a shear wrench or TC gun. This tool is specially designed to grip the nut and the bolt’s spline. These parts are simultaneously torqued. When the correct tension is achieved, the spline will shear off, and the bolt is then properly installed. TC bolts are also pre-lubricated, which is integral to their self-calibrating capabilities.

TC bolts provide a strong hold and a speedier, more consistent installation process compared to structural rivets. They are now used as a standard in many infrastructure applications where rivets would have otherwise been used.

When sourcing A490 TC bolts for construction purposes, some suppliers will continue to specify products under this ASTM spec, however, the American Society for Testing and Material standards organization has withdrawn the A490 bolt spec and now uses F2280 or F3125, which pertain to high strength steel and alloy steel structural bolts.

Bolts used for vital construction settings should always be sourced from reputable fastener suppliers. TC bolts should be tested and confirmed for quality and integrity within specific performance ratings. This is best done by a trusted construction fastener distributor.

Can A490 TC Bolts Be Galvanized? 

Per A490 TC bolts cannot be galvanized. Hot-dipped galvanization or zinc electroplating cannot be done on these bolts to prevent the potential of hydrogen embrittlement. Zinc- or aluminum-based protective coatings are sometimes applied when added corrosion resistance is needed but more often than not, these bolts are kept plain.

What Is The Difference Between A325 TC Bolts And A490 TC Bolts?

A325 TC bolts and A490 TC bolts are very similar with the exception of their material, which then affects their tensile strength capacity. A325 TC bolts are made of medium carbon steel, carbon boron steel, medium carbon alloy steel. A490 TC bolts are made from alloy steel. A490 bolts offer higher tensile strength capabilities compared to A325 TC bolts.